A trivial example of such a method is as follows. (a) Establish a voice path between a first telephone and a second telephone in a telecommunications system where said voice path includes voice compression and decompression (such as a mobile telecommunications system) by taking the first telephone off-hook, dialing the number of the second telephone on the key pad of the first telephone and taking the second telephone off-hook when it rings in response to this dialing. The first telephone and the second telephone are thus involved in a straightforward two-way call in which a first voice path connects the first telephone to the second telephone and a second voice path connects the second telephone to the first telephone. (b) Say "telephone 1" into the microphone of the first telephone; and (c) listen to the loudspeaker of the second telephone for reception of the message "telephone 1" at the second telephone via the first voice path established between the first and second telephones. Since voice compression algorithms used in telecommunications systems with voice compression and decompression are optimized for transmission of human speech, the message "telephone 1", when received at the second telephone, will be recognizable enough to identify the source of the message as the first telephone for a listener at the second telephone already aware that the message "telephone 1" uniquely identifies the first telephone. More complicated examples than the trivial example just given may be constructed by including such features of present-day telecommunications systems as call forwarding, conference calling and call waiting, so that the first telephone and the second telephone may instead be involved in a complex asymmetrical call between more than two telephones.
A variety of known methods of testing voice paths in telecommunications systems where said voice paths include voice compression and decompression have focused on the manual execution of test cases similar to the trivial example just described. Such manual testing involves a human tester speaking into the first telephone and either the same or a different tester listening at the second telephone for reception of the transmitted voice signal. This practice, although easily implemented, has certain problems and disadvantages, mostly arising from the limitations inherent in using a human tester to execute test cases.
Firstly, such manual testing prevents the accurate reproduction of previously conducted test cases. Accurate reproduction of a previously conducted test case may be required when the telecommunications system containing the voice path being tested has been modified or upgraded, and it is required to test for correct functioning of the modified or upgraded system, or that a fault previously present in the unmodified system has been corrected. Such accurate reproduction of a test case may also be required when a previously conducted test case has indicated a fault in the telecommunications system containing the voice path being tested and it is required to repeat the previously conducted test case to help establish the cause of the fault. Especially in the latter case, the reproduction of test cases with a timing as accurate as possible is required, something which manual testing cannot provide.
Secondly, manual testing cannot be used to execute test cases which in themselves require critical timing or accuracy. The execution of test cases requiring such critical timing or accuracy may be required to reveal faults in the telecommunications system containing the voice path being tested which would not otherwise be detectable by executing only approximate test cases.
Thirdly, it is impractical to use manual testing in a variety of situations, such as to execute test cases lasting a long time, where continuous testing of a voice path over a longer period of time, i.e. a period of 24 hours or seven days, may be required to detect faults not detectable by the execution of test cases lasting shorter periods of time. On the other hand, manual testing in itself is inherently time-consuming because the manual execution of a single test case may take many minutes on account of the inherent limitations of human testers. This has the disadvantage that the number of test cases that can be executed in a given period of time is severely restricted.
Finally, manual testing cannot be performed without the presence of a human tester. Thus, manual execution of test cases for testing voice paths in telecommunications systems has certain problems and disadvantages associated with it.
Known methods for testing voice paths in telecommunications systems where said voice paths include voice compression and decompression have also focused on interrogating components of the telecommunications system containing the voice path being tested from a telephone at one end of the voice path using test routines designed for that purpose. In a mobile telecommunications system, for example, the components of the system which are interrogated might include a mobile services switching center (MSC), a base station controller (BSC) and/or a base transceiver station (BTS). However, such interrogation of the components of a telecommunications system has the disadvantage that it only tests a part of a voice path at a time, and does not test a complete voice path from first telephone to second telephone all at the same time. It also has the problem that although such interrogation of the components of a telecommunications system can be used to confirm that the interrogated components function correctly in the test conditions, it cannot be used to confirm that they will function correctly when integrated into the complete voice path.
DE 32 11 967 C2 describes a method of testing the operation of a computer aided communication switching device, especially for traffic-simulation in telecommunication systems. A plurality of connections can be established between pairs of user-simulators and the reaction of the respective telecommunication system can be tested. Further, the transmission of tone pulses between two user simulators, involved in a call, can be observed. However, an identification of the source of the transmitted tone pulses is not performed, since always only two user simulators are connected to each other. The method described in DE 32 11 967 C2 therefore does not allow the required comprehensive testing of voice paths in telecommunication systems.
Thus, known methods for testing voice paths in telecommunications systems with voice compression and decompression have certain problems and disadvantages, and demonstrate the need for an improved method of testing voice paths in telecommunications systems where said voice paths include voice compression and decompression.